poetry2nix: drop unused pkgs.xlibsWrapper import

It's a cherry-pick of upstream
https://github.com/nix-community/poetry2nix/pull/897

Merging this earlier will allow removing `xlibsWrapper` entirely.

pkgs/development/tools/poetry2nix/poetry2nix/overrides/default.nix

···
 
             propagatedBuildInputs = (old.propagatedBuildInputs or [ ]) ++ [
               pkgs.cairo
-              pkgs.xlibsWrapper
             ];
 
             mesonFlags = [ "-Dpython=${if self.isPy3k then "python3" else "python"}" ];